Generally, a vehicle having an internal combustion engine mounted therein is provided with a catalyst device to purify exhaust gas. The catalyst device does not demonstrate its effect unless it is heated to some extent, and accordingly, it is disposed near the internal combustion engine so that it is heated immediately.
However, immediately after the internal combustion engine has just started, i.e., when the catalyst device is still not warm, its purification effect is insufficient. A hybrid vehicle or a similar vehicle having a traveling motor mounted therein has a possibility that it may repeat starting and stopping the internal combustion engine, as required, while it travels. This results in more occasions to start the internal combustion engine while the catalyst device is not warm, and the vehicle may emit exhaust gas containing carbon monoxide, hydrocarbon and the like for increased periods of time.
Accordingly, using electric power to warm the catalyst device before starting the internal combustion engine, is considered. Such a catalyst device is also referred to as an electrically heated catalyst (EHC).
Japanese Patent Laying-Open No. 11-210448 (PTL 1) discloses a hybrid vehicle having an EHC mounted therein.